1. Field of the Invention
The present invention relates to semiconductor light-emitting devices.
2. Background Art
Semiconductor light-emitting devices emitting blue-violet laser beams having a wavelength in the 400 nm band have been developed for use in next-generation DVDs (digital versatile disks) etc. A ridge waveguide semiconductor light-emitting device is known as an example of such devices, with a device structure having, e.g., a double heterojunction on a GaN substrate, the double heterojunction being formed of a material containing a InGaAlN, and having an upper cladding layer in a shape of a ridge (for example, Japanese Patent Laid-Open Publication No. 2000-299497). In this ridge waveguide semiconductor light-emitting device, a non-doped n-type contact layer is formed of Al0.05Ga0.95N on an n-type GaN substrate. An n-type contact layer is formed of Si-doped Al0.05Ga0.95N on the non-doped n-type contact layer. An n-side electrode is formed in a region of the n-type contact layer, and a Si-doped n-type crack prevention layer is formed of In0.08Ga0.92N in the remaining region. A multilayer film having a superlattice structure serving as an n-type cladding layer is formed on the n-type crack prevention layer by alternately stacking non-doped Al0.14Ga0.86N layers and Si-doped GaN layers 160 times. A non-doped n-type guide layer is formed of GaN on the n-type cladding layer. An active layer having a multiple quantum well (MQW) structure is formed on the n-type guide layer by alternately stacking Si-doped In0.01Ga0.99N barrier layers and undoped In0.11Ga0.89N well layers three times and forming a barrier layer thereon. An Mg-doped p-type overflow prevention layer is formed of Al0.4Ga0.6N on the active layer. A multilayer film having a superlattice structure serving as a p-type cladding layer is formed in a ridge shape on the p-type overflow prevention layer by alternately stacking non-doped Al0.1Ga0.9N layers and Mg-doped GaN layers 100 times. A protection layer is formed of a Zr oxide at a side portion of the p-type cladding layer, and an Mg-doped p-type contact layer is formed of GaN on the p-type cladding layer. A p-side electrode is formed on the p-type cladding layer and the protection layer.
Since the band gap of the overflow prevention layer is wide, it is possible to shield electrons implanted from the n-side electrode, and to confine the electrons in the active layer. In order to improve the overflow prevention effect, however, it is necessary to increase the impurity concentration of the overflow prevention layer so as to further widen the band gap. In such a case, there is a problem in that the impurity is diffused into the active layer, thereby inhibiting luminescent recombination and decreasing luminous efficiency.